1. Field of the Invention
The present invention relates to a suction cup, and more particularly, to a dual-layer suction cup capable of adhering to a smooth airtight surface or a rough airtight surface in a press type.
2. Description of the Prior Art
A suction cup is widely used because there is no need for nails and adhesion. Besides, the suction cup won't damage the wall surface and the position of the suction cup can be changed at any time. Most vacuum suction cups on the market only can adhere to a smooth and airtight surface, such as a glass surface or a tile surface.
A conventional suction cup comprises a rubber soft pad disposed in an outer suction body. The bottom of the soft pad has a chamber. The soft pad is pressed to adhere to a working surface through the outer suction body by exhausting the air in the chamber. By the pressure difference inside and outside, the rubber soft pad can adhere to a smooth airtight surface. If the working surface is a rough airtight surface, the rubber soft pad cannot seal the rough airtight surface, which results in that this kind of suction cup cannot be used.
An improved suction cup is provided with an air-extracting structure to enhance its adhesion effect. But, it cannot attach to a rough airtight surface, either. This suction cup is complicated and has a high cost, so it cannot be used widely. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve this problem.